Flexible mandrel



Jan. 8, 1957 L.. E. ZERLAUT FLEXIBLE MANDREL Filed March 24, 1955 IN VEN TOR. LEONARD E. 25m/:ur v WW United States Patent() FLEXIBLE MANDREL Leonard E. Zerlant, Santa Ana, Calif. Application March 24, 1955, Serial No. 496,379 e Claims. (Cl. 153-63) This invention relates to exible mandrels, and more particularly to an improved exible mandrel adapted to be inserted Within tubes and pipes to enable the bending thereofwhile preventing any objectionable deformation, such as kinking, of the tube or pipe.y

The invention relates to a flexible mandrel of the general type shown in the patent to Stjarnstrom 1,856,597, i. e. a mandrel comprising a non-flexible portion adapted to be attached to a tube bending machine, a flexible por tion comprising a cable and a plurality of complementary shaped spherical rings disposed thereon, an outer member xedly attached to one end of the cable andserving as a retainer member for said rings, and means comprising a plug attached to the other end of the cable threadably engageable with saidnoneexible portion.

The improvements over the mandrel of the mentioned patent comprise: the provision of .cable-bearing inserts for the spherical rings adapted to center said rings on the cable and to cause said rings to efficiently articulate with respect to each other in response to bending movement of the cable; and the provision of means comprising split cable-bearing inserts enabling ready addition of spherical rings to the cable or removal therefrom, or the replacement of said rings with rings of diiferent size, without the necessity of disassembling the cable assembly or of even disattaching said assembly from the nonllexible portion of the mandrel,

Various other objects and advantages of the invention will be apparent from the following description taken in conjunction with the drawing for-ming part of this specification, and in which:

Figure l is a view in diametral section of the improved mandrel of the invention;

Figure 2 is a view in diametral section of a portion of the mandrel, the same being shown within a bent tube;

Figure 3 is an attenuated view in perspective showing one of the spherical segments, which has been broken away for clarity of detail, and a split insert therefor; and

Figure 4 is a view in diametral section showing the complemental relationship of a pair of spherical semments.

With reference to the drawing, the mandrel comprises a non-flexible cylindrical portion 10 having a partially internally threaded bore 12 and an internally threaded counterbore 14, the latter being adapted to be Vsecured to an externally threaded spindle of tube bending apparatus, not shown, an externally threaded plug 16 adjustably disposed within bore 12 and having a cross slot 18 in the end thereof whereby said plug may be positionally adjusted rotatably by a screw driver, a llexible cable 20 having an end thereof iixedly secured within plug 16 and having xedly secured to the other end thereof a cylindrical retainer member 22, inserts indicated generally at 24, 26 and 28 disposed in sleeved relation to cable 20, and a plurality of spherical rings 30 sleeved on inserts 26 and 28. The mandrel is further provided with a set screw 32 carried by the cylindrical portion 10 and adapted 2,776,697 Patented Jan. l8, 1957 2 to secure plug 16 against rotation when the latter has been adjusted to a desired position.

The end surface 34 of the cylindrical portion 10 andthe external surfaces 36 of the rings 30 are spherical segments in form, as are the inner rearwardly directed surfaces 38 of the rings, with said surfaces being complemental to each other, as indicated in Figure 4.

The inserts 26 for the rings 30 are comprised of two half sections 40 and 42, as shown in Figure 3, and said inserts are provided with anges 44 at one end adapted to seat against inwardly directed annular shoulders 46 formed on the rings 30. The rearwardly directed ends of the inserts 26 and the insert 28 are tapered, as indicated at 48. Insert 2S, which, like the inserts 26, is formed of two half sections, is provided with a flanged end S0 which is deeper than the flanges 44 of inserts 26, with said flanged end 50 being provided in its forward face with an annular concavity 52 adapted to seat the annular convex peripheral end portion 54 of retainer memher 22. Insert 24, likewise formed of two half sections, has a non-tapered rearward end 56 adapted to fit within the outer and non-threaded end portion 58 of bore 12 and has a ange 60 adapted to engage shoulder 62 formed in the cylindrical portion 10 of the mandrel.

The end surface 62 of the cylindrical portion 10 of the mandrel and the end surfaces 64 of the rings 30 are dished inwardly, while the ring are also provided with complemental dished surfaces 66. When the surfaces 64 are all brought into contact with their associated surfaces 66 along lines of mutual engagement, as shown in the underside of Figure 2, wherein the mandrel is disposed within a tube 68 which has been bent, the mandrel is locked against further bending in the same direction and in the same plane, i. e. the plane mutually occupied by all of the lines of engagement of surfaces 64 and 66. It will be appreciated that the mandrel, as shown in Figure 2, is universally movable in every direction but further straight downwardly.

In effect, the inserts, and particularly the inserts 26 and 28, which move with the cable, constitute the centering means and the means for movably attaching the discs to the backbone, i. e. the rings 30 to the cable 20, for ready and eliicient vertebral movement.

Rings 30 can be added to or removed from the mandrel, or rings of one size can be substituted for another, by the simple expedient of rotating the plug 16 to move it toward the forward end of the cylindrical portion 10, without moving the plug out of threaded engagement with bore 12. For example, to remove the leading ring, it is only necessary to loosen the ring assembly in this manner a sufcient degree to enable the removal from between said ring and the retainer member 22 of the two half sections of the insert 28. The leading ring is then slipped over the member 22, since the rings 'have a larger internal diameter than the outside diameter of the retainer member. The two half sections of the first of the inserts 26 are then removed and replaced with the half sections of an end insert 28, and the plug 16 is then threaded inwardly of mandrel portion 10 to bring the ring assembly to the end-wise tightened condition of Figure 1, in which condition the rings will readily slide over each other in a vertebral action upon a bending of the cable.

It will be appreciated that the bending of the cable causes the llanges 44 and 50 of the inserts 26 and 28 to positively pivot the rings relative to each other, while the rings remain individually centered with respect to the cable, by the engagement between said anges 44 and 50 and the internal shoulders 46 of the rings.

What is claimed is:

1. A device of the class described comprising a flexible cable, a plurality of rings disposed on said cable, said rings having spherical convex outside and spherical concave inside surface portions whereby said rings maybe disposed in partially overlapping relation for vertebral movement on said cable and means for maintaining said rings in rrn endwis'e engagement without inhibiting Said vertebral movement comprising: an elongated member having a threaded bore, aplug secured to the inner end of said cable' and adjustably disposed in threaded relation within said bore, a retainer member secured to the outer end of said cable, and a sleeve-like insert for each ring disposed concen'trically of each ring in closely embracing relation with said cable, with each ring and insert therefor having complemental ange and shoulder means adapted to impart a positive vertebral movement to said rings upon ilexure of said cable.

2. The device as set forth in claim l, said retainer member having a' maximum transverse dimension less than the minimum internal diametral dimension of said rings, and said inserts being each formed of two complemental half sections, whereby said rings may be removed from said cable" b'y adjusting said plug within said bore to provide a degree of looseness between said rings suiicient to enable the removal from said cable of said inserts.

3. The device as set forth in claim l, said rings having annular dished surface portions at their forward ends and surface portions at their rearward ends complementari to said dished surface portions.

4, The device as set forth in claim 3, said retainer member having a maximum transverse dimension less than the minimum internal diametral dimension of said rings, and said inserts being each formed of two complemental half sections, whereby said rings may be removed from said cable by adjusting said plug within said bore to provide a degree of looseness between said rings suflic'ient to enable the removal from said cable of said inserts.

5. In a device of the class described including a flexible cable', a" plurality of alike rings on' said cabley having spherical convex outside and spherical concave inside surface portions whereby said rings may be disposed in partially overlapping relation for vertebral movement on said cable, an externally threaded plug fixed on one end of said cable, a retainer member for said rings secured to the other end of said cable, and holder means for threadably receiving said plug to place said cable under tension; the provision of sleeve-like inserts for said rings disposed concentrically of said rings in` closely embracing relation withy said cable, said inserts having radially projecting flanges at their forward ends seated on annular shoulders formed on said rings, with the insert disposed adjacent said retainer member being in reacting engagement with the rearward end thereof.

6. In a device of the class described as set forth in claim 5, said rings being adapted to be passed over said retainer member, and said inserts being formed of two complemental half sections for placement on and removal from said cable without necessitating the removal of said plug or said retainer member from said cable.

References Cited in the le of this patent UNITED STATES PATENTS 174,609 Wright Mar. 7, 1876 279,573 Leaycraft June 19, 1883 650,049 Lynch May 22, 1900 1,683,573 Mueller et al. Sept. 4, 1928 1,748,158 Walp Feb. 25, 1930 1,856,597 Stjarnstrom May 3, 1932 2,425,298 Attridge et al Aug. l2, 1947 2,451,717 Check Oct. 19, 1948 2,453,531 Meyers Nov. 9, 1948 

